jsontreemodel.h

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/*\
 * Copyright (c) 2018 Sze Howe Koh
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
\*/

#ifndef JSONTREEMODEL_H
#define JSONTREEMODEL_H

#include <QAbstractItemModel>
#include <QJsonObject>
#include <QJsonArray>

//=================================
// JsonTreeModelNode and subclasses
//=================================
/*
    If only we could get a QJsonValueRef to a nested item,
    we wouldn't need such "heavy" node classes...
*/
/*
    TODO: Support user-defined Structure and Scalar column names
    TODO: Support user-defined icons for different datatypes in Structure column???
    TODO: Support user-defined font for Array indices in Structure column???
*/
class JsonTreeModelNode
{
public:
    enum Type {
        Scalar, 
        Object, 
        Array   
    };

    JsonTreeModelNode(JsonTreeModelNode* parent) : m_parent(parent) {}
    virtual ~JsonTreeModelNode() {}

    inline JsonTreeModelNode* parent() const
    { return m_parent; }

    inline void setParent(JsonTreeModelNode* parent)
    { Q_ASSERT(parent->type() != Scalar); m_parent = parent; }

    virtual Type type() const = 0;
    virtual QJsonValue value() const = 0;

private:
    // NOTE: Only JsonTreeModelListNode can be a parent, but I don't want to introduce a dependency to a subclass
    JsonTreeModelNode* m_parent;
};

class JsonTreeModelScalarNode : public JsonTreeModelNode
{
public:
    JsonTreeModelScalarNode(const QJsonValue& value, JsonTreeModelNode* parent);

    QJsonValue value() const override
    { return m_value; }

    void setValue(const QJsonValue& value)
    { m_value = value; }

    Type type() const override
    { return Scalar; }

private:
    QJsonValue m_value;
};

class JsonTreeModelListNode : public JsonTreeModelNode
{
public:
    JsonTreeModelListNode(JsonTreeModelNode* parent) : JsonTreeModelNode(parent) {}
    JsonTreeModelListNode(const QJsonArray& array, JsonTreeModelNode* parent);

    ~JsonTreeModelListNode() override
    {
        // TODO: Tell parent to remove this child from its list? Only if we do partial deletions
        qDeleteAll(m_childList);
    }

    inline JsonTreeModelNode* childAt(int i) const
    { return m_childList[i]; }

    inline int childCount() const
    { return m_childList.count(); }

    inline int childPosition(JsonTreeModelNode* child) const
    { return m_childPositions.value(child, -1); }

    Type type() const override
    { return Array; }

    QJsonValue value() const override;

protected:
    void registerChild(JsonTreeModelNode* child);
    void deregisterChild(JsonTreeModelNode* child);

private:
    QVector<JsonTreeModelNode*> m_childList;
    QMap<JsonTreeModelNode*, int> m_childPositions;
};

class JsonTreeModelNamedListNode : public JsonTreeModelListNode
{
public:
    JsonTreeModelNamedListNode(const QJsonObject& object, JsonTreeModelNode* parent);

    inline QString childListNodeName(JsonTreeModelNode* child) const
    { return m_childListNodeNames[child]; }

    inline int namedScalarCount() const
    { return m_namedScalarMap.size(); }

    inline QJsonValue namedScalarValue(const QString& name) const
    { return m_namedScalarMap[name]; }

    inline void setNamedScalarValue(const QString& name, const QJsonValue& value)
    {
        Q_ASSERT(value.type() != QJsonValue::Undefined && value.type() != QJsonValue::Array && value.type() != QJsonValue::Object);
        m_namedScalarMap[name] = value;
    }

    Type type() const override
    { return Object; }

    QJsonValue value() const override;

private:
    // TODO: Use JsonTreeModelListNode::childPosition() for indexing; not need for map with m_childListNodeNames
    QMap<JsonTreeModelNode*, QString> m_childListNodeNames;
    QMap<QString, QJsonValue> m_namedScalarMap;
};

class JsonTreeModelWrapperNode : public JsonTreeModelListNode
{
public:
    JsonTreeModelWrapperNode(JsonTreeModelNamedListNode* realNode);

    QJsonValue value() const override
    { return childAt(0)->value(); } // ASSUMPTION: A wrapper node will always have exactly 1 child JsonTreeModelNamedListNode
};


//=================================
// JsonTreeModel itself
//=================================
class JsonTreeModel : public QAbstractItemModel
{
    Q_OBJECT

public:
    // TODO: Add flag to sort the keys, or leave them in the order of discovery
    enum ScalarColumnSearchMode
    {
        NoSearch,
        QuickSearch,
        ComprehensiveSearch
    };

    explicit JsonTreeModel(QObject* parent = nullptr);
    ~JsonTreeModel() override { delete m_rootNode; }

    // Header:
    QVariant headerData(int section, Qt::Orientation orientation, int role = Qt::DisplayRole) const override;

    // Basic functionality:
    QModelIndex index(int row, int column, const QModelIndex& parent = QModelIndex()) const override;
    QModelIndex parent(const QModelIndex& index) const override;

    int rowCount(const QModelIndex& parent = QModelIndex()) const override;
    int columnCount(const QModelIndex& parent = QModelIndex()) const override;

    QVariant data(const QModelIndex& index, int role = Qt::DisplayRole) const override;

    // Editable:
    bool setData(const QModelIndex& index, const QVariant& value, int role = Qt::EditRole) override;
    Qt::ItemFlags flags(const QModelIndex& index) const override;

    // API specific to JsonTreeModel:
    void setJson(const QJsonArray& array, ScalarColumnSearchMode searchMode = QuickSearch);
    void setJson(const QJsonObject& object, ScalarColumnSearchMode searchMode = QuickSearch);
    QJsonValue json(const QModelIndex& index = QModelIndex()) const;

    // TODO: Decide if the json()/setJson() API should be symmetrical or not

    void setScalarColumns(const QStringList& columns);
    QStringList scalarColumns() const { return m_headers.mid(2); }

private:
    bool isEditable(const QModelIndex& index) const;

    JsonTreeModelListNode* m_rootNode;
    QStringList m_headers;
};

#endif // JSONTREEMODEL_H